Gravitational Displacement Apparatus for treating Sustained Casing Annulus Pressure and Surface Casing Vent Flow

ABSTRACT

An apparatus and method for treating sustained casing annulus pressure (SCP) and surface casing vent flow (SCVF) by continually and consistently injecting higher density fluid into the annulus of a well, wherein the higher density fluid will slowly migrate downwards and displace lower density fluids and gasses due to the pull of gravity, thus helping to control or eliminate SCP by creating the hydrostatic column in the annulus.

FIELD OF THE INVENTION

This invention relates in general to well remediation systems in the oiland gas industry, and in particular to the apparatus and methods usedfor filling an annulus in a well with high density brine, or othersimilar media, to control or eliminate sustained casing pressure.

BACKGROUND

Sustained casing pressure (SCP) and surface casing vent flow (SCVF) isexhibited by many wells and is a large-scale problem in the oil and gasindustry worldwide. It presents safety hazards, regulatory concerns andenvironmental impacts. A failure to manage casing annulus pressures mayresult in well blowouts or other events that may cause significantdamage to property, the environment, and personnel.

In the petroleum industry, oil and gas wells have multiple casings ofdifferent sizes that are suspended from a wellhead. SCP is often causedby persistent gas and liquid migration through the leaking cement sheathin a well's casing annuli, but can also be caused due to, but notlimited to, leaks in casing wellhead seals or poor primary cement job.

In some jurisdictions, wells are operated with a surface casing vent inthe open position. A well that has a leak or exhibits SCP, may alsoexhibit surface casing vent flow (SCVF) if the fluid or gas entering theannulus is allowed to escape through the surface casing vent andreleased into the atmosphere, causing environmental damage.

To control the annular pressure, the “bleed-and-lube” method is oftenused in the industry. This typically involves rigging up to a well andpumping high-density fluid, typically brine, into the annulus throughone vent at the upper end of the well, then bleeding off lighter fluidand gas using a second well valve, which gets displaced when heavy brinemigrates downward. This technique is time consuming, expensive, and maynot get the pressure under control if incorrectly administered by afield engineer or a service company.

DESCRIPTION OF RELATED ART

Another method of SCP remediation utilizes a CARS unit (Casing AnnulusRemediation System, U.S. Pat. No. 6,186,239B1), which pumps high-densityfluid into the annulus using a pressurized tube through an access portin the wellhead. However, in addition to multiple steps and equipmentrequired, this system is relatively impractical because the deliverytube typically encounters various obstacles, making it difficult toinsert deep into the annulus. Further, if the casing itself is cementedto the surface, the tube cannot be inserted to the annulus at all,limiting its use.

Other SCP remediation methods focus on the composition of high-densityfluids by adding various additives to prevent the fluid from dissipatingor mixing with the lighter density fluid.

BRIEF SUMMARY OF THE INVENTION

This apparatus and method addresses the ongoing industry need for aneffective, cost efficient and low maintenance remediation process tomanage SCP and SCVF within an annulus.

This apparatus, placed on the ground slightly above the well withequipped support stands, attaches to two well valves using standardindustry piping and connectors. Once the pressure vessel is filled withhigh-density brine or other similar media, the equipped needle valve isopened, allowing pressure to equalize between the well annulus and thevessel. The brine will then start to drip feed into the casing annulusby gravitation, without the need for a pump. The drip rate can beadjusted by the needle valve. As the brine slowly migrates downward, itdisplaces lighter fluids and gases, which rise up the annulus column andeventually through the second valve back into the vessel, to be bled offupon refill with more high density brine.

In the preferred method, the high-density brine is drip fed into thecasing annulus using the equipped needle valve with sight. By decreasingthe flow, the brine is allowed to slowly absorb and migrate downwardswithout dispersing out of the second valve. This method allows for theuse of any type of high-density brine, without the need for any specifictype of formulation.

The pressure vessel can be of any shape (ex. sphere, cylinder, cube) andany size. The size of the vessel would determine the amount of brine itcan store, thereby requiring fewer refills and/or faster drip rate. Theapparatus may further optionally have a digital fluid level sensor withwireless connection to notify an operator when a refill is required.

These and other features of the present invention are more fully setforth in the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing illustrates an example of the apparatus, in theshape of a cylinder, coupled to a wellhead assembly.

DETAILED DESCRIPTION

The apparatus and method of the present invention will now be describedmore fully hereinafter with reference to the accompanying drawings inwhich some, but not all, embodiments of the invention are shown. Indeed,various embodiments of the invention may be embodied in many differentforms and should not be construed as limited to the embodiments setforth herein; rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the invention to those skilled in the art. Like numbers referto like elements throughout. For the convenience in referring to theaccompanying FIGURES, directional terms are used for reference andillustration only. For example, the directional terms such as “upper”,“lower”, “above”, “below”, and the like are being used to illustrate arelational location.

Referring to the accompanying drawing, the pressure vessel in the shapeof a cylinder 2 is placed on the ground next to a well 4 with theequipped support stands 1, such that it sits slightly higher than thewellhead valves 5 and 6. Using standard industry piping and fittings 3,the cylinder connects to a well through two outlet wellhead valves, intoone of which the higher density fluid is injected 5 and from the other 6where the lower density fluid and gasses are returned back into thecylinder through displacement, to be bled and withdrawn upon refill. Thecylinder has a minimum of two connections, one lower 7, from which thehigher density fluid flows through the piping 3 and into the wellheadvalve 5, and one higher 8, into which lower density fluid and gasses arereturned back into the cylinder from the second wellhead valve 6.

The larger the cylinder, the greater the volume of brine it can store,which allows for less frequent refills and bleed offs.

Once filled with high-density brine or other similar media through fillvalve 9, the equipped needle valve with sight 10 is opened and adjustedto allow the brine to drip feed into the casing annulus by gravitationthrough the well valve 5. The rate of drip feed is can be adjusteddepending on the type of well and its immediate requirements.

As the brine slowly migrates downward and deep into the casing annulus,it fills up micro channels and cracks along the way, displacing lighterfluids and gases. By raising the density and hydrostatic pressure in thefluid column, the casing annulus pressure is brought under control orinto regulatory compliance. The displaced lower density gasses andfluids rise to the top of the wellhead, then exit from the second wellvalve 6 and back into the cylinder through the higher connection 8. Oncein the cylinder, the lighter density fluid will be bled off uponrefilling with more high-density brine. Using a lower bleed valve 11 atthe lower connection on the cylinder, the lower density fluid isdrained. Once the bleed process is complete, the cylinder is refilledwith high-density brine using the fill valve 9. A fluid level indicator12 is used to visually determine when the cylinder needs to be refilled.Optionally, the fluid indicator can be digital with informationtransmission capability. The apparatus also includes industry standardpressure gauge 13 and an optional flow indicator 14, which can measureand record volume of fluid injected.

It should be noted that a well may have more than two wellhead valves,depending on the number of casings a well contains. Therefore theapparatus should be connected to the valves where SPC is exhibited.

Generally it should be appreciated by one of skill in the art that manyindustry standard high-density fluids could be used with this apparatus,therefore not limited to any specific formulation. These fluids aregenerally comprised of liquid brine, including halide brines, formatebrines, and acetate brines and may include additional additives andmodifiers to meet specific needs and requirements.

This invention has significant advantages to current systems andmethods. Once initially set up on site next to a well, the remediationprocess can be continual and consistent without the need for periodicmanual ‘bleed-and-lube’ process from a field operator, thereby reducingcost, time and without production interruption. Depending on size, theapparatus is relatively mobile and can be placed on any well site,including wells in remote locations and can be left on site as long asneeded. Additionally, the apparatus can be placed on non-producingabandoned wells, which typically get overlooked because of high costsinvolved in the traditional process, thereby reducing environmentalimpact and meeting regulatory requirements at minimal cost, with theadded benefit of powerless operation due to gravity.

It is to be understood that the subject of the present disclosure isintended to demonstrate a preferred embodiment of the invention and isnot limited to the exact details of construction, operation, exactmaterials, or embodiments shown and described, as modifications andequivalents will be apparent to those skilled in the art. As such, thetechniques disclosed in the description represent techniques discoveredby the inventors to function well in the practice of the invention, andthus can be considered to constitute preferred modes for its practice.However, those of skill in the art should, in light of the presentdisclosure, appreciate that many changes can be made in the specificembodiments which are disclosed and still obtain a like or similarresult without departing from the scope of the invention. For example,in an alternative embodiment, a pump can be used to assist the injectionof high-density fluid into the well valve, without needing the apparatusto be lifted higher such that the fluid will flow due to gravity alone.Accordingly, the subject disclosure is therefore to be limited only bythe scope set out in the following claims.

What is claimed is:
 1. An apparatus for treating sustained casingannulus pressure (SCP) and surface casing vent flow (SCVF) by deliveringhigh density fluid through gravitation, said apparatus comprising: apressure vessel capable of holding fluid, said vessel be pressure ratedto meet wellhead requirements, and said vessel have a minimum of oneconnection port at the bottom and one connection port at the top;adjustable stands to mount the vessel; standard piping and fittings toconnect the vessel to two wellhead valves; needle valves; secondaryvalves attached to both connection ports on the vessel; pressure gauge;fluid level indicator.
 2. An apparatus according to claim 1 wherein: theapparatus contains an optional pump to assist with pumping the highdensity fluid if gravitational setup is not possible due to well designand location.
 3. An apparatus according to claim 1 wherein: the needlevalve contains an optional sight glass for visual drip feed control. 4.An apparatus according to claim 1 wherein: the pressure vessel can be ofany shape or size.
 5. An apparatus according to claim 1 wherein: thefluid level indicator can include, but not limited to, a sight glass,magnetic, or digital with or without information transmissioncapability.
 6. An apparatus according to claim 1 wherein: the adjustablestands can include wheels for ease of mobility to another well site. 7.A method of using the apparatus in claim 1 to drip feed the high-densityfluid into the wellhead valve and subsequently into the casing annulus.8. A method of using the apparatus in claim 1 on various types of wells,including but not limited to currently producing oil and gas wells,abandoned wells, remote wells.